i would like to ask why i lose?

61.... Qb5+ 62.Kxb5 Rb7 63.a6 Bc3 64.axb7 a6+ 65.Kxb6 Ba5+ 66.Kxa5 a5 67.Kxa5 Kd6 68.b8Q+ and White wins.

That's the rule. ;)

66. Kxa5 a5? A pawn cannot move to an already-occupied square.

Regardless, @alove2kill , what jupp is attempting to say is that if there is a possible continuation of the game where White can checkmate, no matter how unlikely it is, then the game is counted as a loss instead of a draw.

this is a time issue, not a mating issue

You lost because you had no time anymore, why are you asking ?

@alove2kill you lost because time run out and white had a pawn.
If white had insufficient material for a win (a bishop or a knight) it would have ended in a draw.
The pawn isn't insufficient material because it can promote to a piece that can win the game regardless of the fact that in your particular game white had no chance of winning.